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Finding the Fourth Proportional to 420.40, 580.08 and 280.72

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Solution

The fourth proportional to 420.40, 580.08 and 280.72 is: 387.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.40 : 580.08 = 280.72 : x
  2. Step 2: Convert to fraction form
    420.40/580.08 = 280.72/x
  3. Step 3: Cross multiply
    420.40x = 580.08 × 280.72
  4. Step 4: Simplify right side
    420.40x = 162,840.06
  5. Step 5: Solve for x
    x = 162,840.06/420.40
  6. Step 6: Final answer
    x = 387.35

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.